This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-200252, filed Jun. 30, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a method for cleaning the surface of a to-be-processed semiconductor substrate in a lithography process, and more particularly to a substrate process method for use in a rinsing process executed after a resist developing process using a liquid developer.
In accordance with recent developments in LSI micro pattern fabrication, there have been increasing demands for stricted specifications regarding the amount of resist residues (hereinafter referred to as xe2x80x9cdefectsxe2x80x9d) on a semiconductor substrate found in a rinsing process executed after a resist pattern developing process, as well as calls for greater controllability of the size of the resist pattern formed on the semiconductor substrate. In a rinsing process executed after a resist developing process in the conventional lithography process, deionized water (DIW) is generally used as a rinsing liquid. However, the rinsing method using only deionized water is insufficient at completely eliminating all resist residues or defects, since the rinsing power of deionized water is not so strong.
To solve this problem, a rinsing method of reapplying a liquid developer to a substrate after the usual developing process has been employed recently. This method is contrived in light of the fact that the main cause of the occurrence of defects is xe2x80x9cpH shockxe2x80x9d in which resist-dissolved products in a liquid developer are separated as the resist residues in a rinsing liquid as a result of an abrupt reduction in pH, that appears at the changeover from the developing process to the rinsing process. In the method, defects or resist residues are dissolved in the resupplied liquid developer and eliminated together with the liquid developer, thereby reducing the number of defects which may occur when deionized water is applied in the next process.
Although this method can significantly reduce the number of defects, depending upon the combination of the resist and liquid developer the controllability of pattern dimensions may degrade, since the resupplied fresh developer is added at the point in time close to the termination of the developing process. This may increase the degree of variation in the size of resist patterns formed on the substrate.
As described above, the conventional rinsing method, which uses only deionized water in a rinsing process executed after a developing process, is limited in its power to lower the number of defects. Further, in the other conventional method of reapplying a liquid developer to a substrate after the developing process using a first supplied liquid developer is terminated, although the number of defects can be significantly reduced, the controllability of the resist pattern size is degraded, with the result that the degree of variation in the sizes of resist patterns formed on the substrate is increased.
The present invention has been developed in light of the above problems, and has its object to provide a substrate process method capable of significantly reducing the number of defects that may occur after a developing process, without increasing the degree of variation in the size of a resist pattern.
To satisfy the object, one aspect of the present invention provides a substrate processing method for developing, using a liquid developer, a resist film formed on a to-be-processed substrate and having a desired pattern created by exposure, and then rinsing an exposed surface of the substrate, comprising: a first rinsing step of rinsing the exposed surface of the substrate using water that contains an oxidizing gas, thereby decomposing organic matter sticking to the exposed surface of the substrate; and a second rinsing step of rinsing the exposed surface of the substrate using water that contains a deoxidizing gas, thereby removing the decomposed organic matter.
Another aspect of the present invention also provides a substrate process method of developing, using a liquid developer, a resist film formed on a to-be-processed substrate and having a desired resist pattern created by exposure, and then rinsing an exposed surface of the substrate, comprising: a first rinsing step of rinsing the exposed surface of the substrate using water that contains an oxidizing gas, thereby decomposing organic matter sticking to the exposed surface of the substrate; and a second rinsing step of rinsing the exposed surface of the substrate using water that contains ammonia, thereby removing the decomposed organic matter.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.